1. Field of the Invention
The invention describes a hybrid automatic gain control (AGC) method and apparatus suitable for normalizing (by attenuation or amplification) dynamic range of analog input signal.
2. Description of Related Art
In conventional automatic gain control (AGC) systems, an input analog signal is normalized in either the analog domain or the digital domain. Conventional AGC is performed by measuring a particular parameter of the input analog signal (i.e., the sync height of a composite video signal, for example) and based on that measurement, the desired gain is calculated and applied to the input signal. In the digital domain, AGC implemented using a feed-forward type arrangement whereas in the analog domain, a feedback system is employed. Although digital domain type AGC is inexpensive to implement and fast, the output signal can exhibit coarse granularity due to the discrete nature of the multiplication in the digital domain. Even though AGC in the analog domain is continuous in nature, analog AGC is costly to implement and is subject to a very slow response, or oscillations, when confronted with sudden changes in the input signal.
Therefore, what is desired is a cost effective, system, method, and apparatus for providing both fast and high resolution automatic gain control (AGC).